Ionized gas electrostatic copyboard



Oct. 14, 1969 G. F. BARNETT 3,473,097

IONIZED GAS ELECTROSTATIC COPYBOARD Filed sept. 23, 1968 v 2sheets-sheet 1 nnnn /Na/wro/P sur F. HARA/Err' afi;

Oct. 14, 1969 G. F. BARNETT IONIZED GAS ELECTROSTATIC COPYBOARD 2Sheets-Sheet L Filed Sept. 23, 1968 a f/ fr0/mfr United States Patent O3,473,097 IONIZED GAS ELECTROSTATIC COPYBOARD Guy F. Barnett,Warminster, Pa., assignor to The Simco Company, Inc., Lansdale, Pa., acorporation of Pennsylvania Filed Sept. 23, 1968, Ser. No. 761,426

Int. Cl. H05f 1/02, 3/06 U.S. Cl. 317-262 Claims ABSTRACT 0F THEDISCLOSURE An electrostatic copyboard in which a wire network to which ahigh voltage D.C. generator is coupled is adjacently spaced in a gasfrom the surface of a dielectric panel. The corona discharge from thefine wires causes the gas, such as air, in the gap to become conductive,and the gas ions contact and deposit on the adjacent surface of thedielectric panel causing it nominally to approach the wire potential. Anarticle abutting the opposite surface of the dielectric panel andgrounded is electrostatically adhered thereto. Heating the gas improvesadhesion.

This invention relates to electrostatic holding devices and moreparticularly relates to electrostatic copyholders, such as are commonlyused for holding articles, sheets and film preparatory to photographingand/or xerographmg.

In prior U.S. Patent No. 3,359,469, there is shown and described anelectrostatic copyboard in which a high voltage D.C. potential isapplied to a conductive plate in contact with the back surface of aninsulative panel. By abutting an article against the front workingsurface of the insulative panel and providing a conductive path from thearticle to the other side of the high voltage, the articleelectrostatically adheres to the working surface with great tenacity.The foregoing electrostatic copyboard is known as a front lighted systemsince the conductive plate used is opaque.

A backlighted copyboard is one in which light is directed from the rearof the copyholder and through the work supporting panel so as toilluminate semitransparent articles, such yas photographic or X-rayfilm, or to perform reproduction operations through a transparent plate,such as in photographic printers or Xerographic copiers. Initialattempts to incorporate la transparent conductive coating upon atransparent dielectric plate have resulted in failures because of thetendency for the coating to break down and erode from the high voltageapplied. Wire mesh screens which have previously been used as aconductive plate for the high voltages interfered considerably with thelight transmission characteristics through the front plate and, inaddition, cast shadows upon or obscured the characters or indicia on thearticles or sheets to be reproduced. When liquids such as water or othersolutions were employed as the transparent conductive member in abutmentwith the dielectric work supporting panel, considerable sealing problemsarose because of the pressures developed by the hydraulic heads,especially when the copyboards weer placed in upright position.

The present invention overcomes all of the foregoing problems anddiiculties through the use of a single fine wire or a selected minimumnumber of fine wires which `are formed into a network or reticle of anydesired pattern wherein the areas between adjacent wires are extremelylarge (inches) as compared to the wire diameter (1 or 2 mils). The wirenetwork is adjacently air spaced from a dielectric panel or gasencapsulated in spaced dis- 3,473,097 Patented Oct. 14, 1969 ICCposition from a dielectric work supporting panel or between a pair ofsuch panels separated from each other by a gap. A high D.C. voltageapplied to the wire network creates a corona discharge from the finewire, which acts as an innite number of points and causes the gas tobecome conductive. The gas ions which are created are deposited on theadjacent surfaces of the dielectric panel as well as on surfaces remotefrom the wires whereby the surfaces become charged nominally to the samevoltage as that imposed on the wire network. Hence, an article placed inabutment with the front working surface can be made to electrostaticallyadhere thereto. Since the wire used is extremely fine, approximately 2mils or less, and since they are spaced from each other by a relativelylarge distance, approximately 2 inches, they are essentially invisibleand do not materially interfere in any appreciable way with transparencyor translucency of the dielectric panels themselves. Hot gas, such asair, can be directed through the channel between two adjacently spaceddielectric panels or against the work supporting panel so as to heat anddrive off any film of moisture which might otherwise diminish thesurface resistivity of the working surface and interfere with adhesion.

It is therefore an object of this invention to provide an electrostaticcopyboard which is well adapted for transparent or translucentbacklighting with minimal nterference.

Another object of this invention is to provide an electrostaticcopyboard in which electrostatic adhesion is produced solely by thecreation of gas ions from a high voltage wire network interposed inspaced disposition from the rear surface of a dielectric working panel.

Still another object of this invention is to provide an electrostaticcopyboard which utilizes a gas as the charging medium because of itsability to be heated and circulated against the dielectric working panelso as to drive off moisture which might otherwise reduce surfaceresistivity and interfere with adhesion.

Yet another object of this invention is to provide an ionized gasactivated electrostatic copyboard.

Yet still another object of this invention is to provide anelectrostatic copyboard in which there are no sealing problems.

Other objects of this invention are to provide an improved device of thecharacter described which is easily and economically produced, which issturdy in construction and both highly etlicient and effective inoperation.

With the above and related objects in view, this invention consists ofthe details of construction and combination of parts as will be morefully understood from the following detailed description when read inconjunction with the accompanynig ydrawings in which:

FIGURE 1 is a perspective view of an ionized gas actuated electrostaticcopyboard embodying this invention.

FIGURE 2 is a sectional view taken along lines 2 2 of FIGURE 1.

FIGURE 3 is a fragmentary perspective view of a IStringing element Iforsupporting a network of corona discharge wires in the gas space.

FIGURE 4 is a plan view of the copyboard showing one pattern ofStringing the wire network.

FIGURE 5 is a sectional view taken along lines 5-5 of FIGURE 4.

FIGURE 6 is a plan view of another mode for Stringing the wire network.

FIGURE 7 is a plan view of still another manner of Stringing the wirenetwork in the electrostatic copyboard.

FIGURE 8 is a perspective view of a modified [form of the ionized gaselectrostatic copyholder in which hot airis circulated in theinterspace.

FIGURE 9 is a perspective view of the electrostatic copyboard in whichthe front surface is heated by a radiant panel.

Referring now in greater detail to the drawings in which similarreference characters refer to similar parts, there is shown an ionizedgas electrostatic copyholder which comprises a first dielectric panel A,a second dielectric panel B spaced from the first panel, a conductivewire network C strung in spaced disposition between the interior facesof the front and rear panels, and a high voltage D C. generator Dconnected to the wire network.

While the front and rear panels A and B can be of any insulativecomposition, it is preferable t utilize glass because its volumeresistively lies in a desirable range as compared to most plasticmaterials. In addition, for trans.- parent materials, glass has a higherresistance to scratching than plastic compositions, such as acetates,vinyl or acrylic polymeric substances. The panels A and B can either beopaque, translucent or transparent. For example, where backlighting, onecan use a translucent panel for diffused light as in X-ray viewing.Similarly a transparent panel may be employed for photographic printingor xerographic copying.

The two panels A and B which are in most arrangements identical in planconfiguration are held in spaced disposition from each other 'by anannular insulative frame 12, in this case of rectangular design.However, any peripheral outline may be employed depending upon the needsof the user or the orientation of the exterior panels. In order tostringedly support the Wire network C in any one of a plurality ofpatterns, a conductive comb-like member 14 is secured about the innerperiphery of the annular frame 12 by means of suitable mounting screws16. The comb 14 is preferably in strip form for convenience in cuttingto length and of Phosphor bronze cornposition for both resilience andconductivity. A plurality of claw-like fingers 15 project from the stripand define hooks which permit the wire network to be strung in anyconfiguration. As is apparent, a single wire may 'be stretched fromfingers 15 extending from comb strips 14 at opposite and/or adjacentportions of the annular member 12.

In FIGURE l, the network C constitutes a single wire which extends in aseries of equiangular diagonal lines between the upper and lower combstrips 14. The wire is preferably 2 mil stainless steel for resistanceto corrosion, strength and conductivity, and it is held in a plane whichis approximately one-half inch from the interior surfaces of the panelsA and B. In this embodiment, the lateral strips 14 are not utilized. InFIGURES 4 and 5, a network Cl is illustrated in which the wire is strungin a plurality of spaced parallel lines in rectangular orientationbetween the upper and lower comb members 14. The spacing of the wire isregular and equal and extends across the entire exposed area of theboard in increments of perhaps two inches. In FIGURE 6, there is shown anetwork pattern C2 in 'which the design constitutes a vseries ofirregular diagonal lines adjacent the right and left margins with aclear space in the medial portion. In FIG- URE 7, the network comprisesa latticed pattern C3 arranged with rectilinearly crossing Wires at themargins and extending about a clear zone at the central portion. Manyother variations and combinations of wire networks can be utilizeddepending upon the needs of the ultimate user and his adhesionrequirements.

When the wire network C is suitably coupled to the hot side of apositive or negative high voltage generator, nominally rated at 5,000 to15,000 volts at 2 milliamperes, the relatively small diameter wire actsas though it were an infinite number of points or point sources.Accordingly, the corona discharge from these plural wire point sourcescauses the gas to ionize in the space between the wire network C and theinterior faces of the panels A and B. That is, gasses, such as air,nitrogen, argon and the like, are made conductive by the high intensityelectric field at the fine wires. These ions contact and deposit on theinner surfaces of the dielectric panels A and/or B and within a verybrief time cause the surfaces on which they are deposited to approachthe same potential as that imposed on the wire network C by the highvoltage generator D. By abutting articles, such as a sheet of paperagainst the front surface of either panel and providing a conductivepath from the article to the ground side of the D,C. generator, thearticles are caused to adhere to the work surface of the dielectricpanel.

In FIGURE 8, the interior gap between the panels A and B is coupled to ahot air blower E. The blower E comprises a casing `20 having a fan 22therein. The fan 22 directs air across a series of heating elements 24through an inlet duct 26 formed in the annular frame 12 'between the twodielectric panels A and B. The air from the gap exists through outletduct 28 back into the casing 20 where the fan 22 recirculates the airacross the heating elements 24. Under high humidity conditions, moisturetends to form a relatively conductive film upon the surface of thedielectric panel. The heated air caused evaporation of this film ofmoiseture from the working surfaces of the dielectric panels so as toeliminate its shielding effect. Thus, raising the temperature of thedielectric panels A and B maintains the holding strength of thecopyboard in the presence of high ambient humidity.

In FIGURE 9, the front surface of panel A is heated by a radiant panel30 which evaporates the film of moisture directly rather than throughthe panel from the interior. A lamp 32 is illustrated to represent thebacklighting arrangement, the higher voltage D.C. generator D againbeing coupled to the wire network. Also in FIGURE 9, a sheet 34 ofpaper, for example, is being electrostatically adhered tothe frontsurface of the panel A.

As is apparent from the foregoing description, the instant inventionresides primarily in the use of a fine wire network to which a highvoltage D.C. is connected for producing gas ions in the adjacent space,the ions of like polarity being deposited upon an adjacent dielectricpanel which effectively becomes charged to the same voltage as the D C.generator.

What is claimed is:

1. An electrostatic copyholder comprising a dieelectric panel includinga front working surface thereon, a network of relatively fine wiresadjacently spaced from the rear surface of said dielectric panel with agas gap therebetween, and means for applying a D C. high voltage to saidwire network whereby gas ions produced 'by corona discharge from saidwires will be deposited on the rear surface of said dielectric panel sothat articles placed in abutment with the front working surface areadapted to adhere thereto by electrostatic attraction.

2. The copyholder of claim 1 including a second dielectric paneladjacently spaced from said wire network with a second gas gaptherebetween, the exterior face of said second dielectric panel defininganother working surface against which articles are adapted to adherethereto by electrostatic attraction.

3. The copyholder of claim 2 including means to heat the dielectricpanels.

n 4. The copyholder of claim 1 wherein the gas in the gap 1s air.

5. The copyholder of claim 1 wherein the dielectric panel is glass.

6. The copyholder of claim 3 wherein the means to heat comprises meansto circulate hot gas in the gap between the panels.

7. The copyholder of claim 1 wherein said network lies in a planeparallel to the adjacent surface.

8. The copyholder of claim 7 wherein said network comprises a pluralityof wire elements spaced from each other at regular intervals.

9. The copyholder of claim 7 wherein the wire elements are more closelyspaced in one zone and have an open area in another zone.

6 10. The copyholder of claim 1 wherein said dielectric 3,289,060 11/1966 Rubin 317-262 panel is transparent. 3,359,469 12/1967 Levy et al.317--262 References Cited LEE T. HIX, Primary Examiner UNITED STATESPATENTS 5 D. J. HARNISH, Assistant Examiner 2,742,814 4/1956 Gage 355-32,834,132 5/1958 Taylor et a1 40 125 U-SC1XR- 3,273,301 9/1966 AndersonS17-3X 4o 125;95.85;355-3

